Bring a large pot of water to a boil over high heat. Meanwhile, cut top off peppers 1 inch from the stem end, and remove seeds. Add several generous pinches of salt to boiling water, then add peppers and boil, using a spoon to keep peppers completely submerged, until brilliant green (or red if red peppers) and their flesh slightly softened, about 3 minutes. Drain, set aside to cool.

Preheat oven to 350 degrees F. Heat 4 tbsp of the oil in a large skillet over medium heat. Add onions and cook, stirring often, until soft and translucent, about 5 minutes. Add the garlic and cook a minute more. Remove skillet from heat, add meat, rice, tomatoes, and oregano, and season generously with salt and pepper. Mix well. (You may find it easier to put the ingredients at this point into a large bowl and mix together with your hands.)

Drizzle remaining 1 tablespoon of olive oil inside the peppers. Arrange the cut side of the peppers up in a baking dish, then stuff peppers with filling. Combine ketchup, Worcestershire sauce, Tabasco sauce, and 1/4 cup of water in a small bowl, then spoon over filling. Add 1/4 cup of water to the baking dish. Place in oven and bake for 40-50 minutes (or longer, depending on how big the peppers are that you are stuffing), until the internal temperature of the stuffed peppers is 150-160°F.